A storage system includes a host and a storage apparatus connected to the host. The storage apparatus may be connected to multiple hosts. If the storage apparatus includes multiple control modules (hereafter referred to as “CMs”) each including a piece of firmware and the pieces of firmware are replaced in a hot swapping manner, the CMs are divided into the first part and latter part and these parts separately perform firmware replacement. For example, if the storage apparatus includes four CMs, first, two of the four CMs perform firmware replacement simultaneously. Then, the remaining two CMs perform firmware replacement. The storage apparatus and the host are connected via multiple paths and each path is connected to a corresponding CM. Thus, the firmware is replaced in a hot swapping manner without having to stop operation. Hereafter, an example in which hot swapping firmware replacement is performed in a unit including two CMs will be explained.
FIGS. 1A to 1G are diagrams illustrating firmware replacement according to a related-art example. FIG. 1A to 1D are a diagram illustrating a case where firmware is replaced normally according to a related-art example. This storage system includes a host and a storage apparatus having two paths connected to the host. As illustrated in FIG. 1A, in a normal state, data is transferred from the host to the storage apparatus via one path. Another path is on standby.
As illustrated in FIG. 1B, during replacement of firmware installed on the first part (CM0), data is transferred between the host and storage apparatus via a path connected to the latter part, CM1.
As illustrated in FIG. 1C, during replacement of firmware installed on the latter part (CM1), data is transferred between the host and storage apparatus via the path connected to the CM0 that has performed the firmware replacement.
As illustrated in FIG. 1D, upon completion of the firmware replacement in the latter part (CM1), data is transferred via the path connected to the CM0.
FIG. 1E to 1G are a diagram illustrating a case where an abnormality occurs during replacement of firmware according to a related-art example. If there is an abnormality in one path and if firmware is replaced in a hot swapping manner via another normal path, none of the paths between the storage apparatus and the host can be used as a path for processing an operation. Therefore, the operation stops. FIG. 1E illustrates examples where there is already a failure in the connectivity of the path connected to the latter part, CM1, when firmware replacement is started in the first part, CM0.
As illustrated in FIG. 1E, an abnormality has already occurred in the path connected to the latter part (CM1) before firmware is replaced. Data is being transferred by the CM0.
As illustrated in FIG. 1F, when firmware replacement is started in the first part (CM0), data can no longer be transferred via the path connected to the CM0.
As illustrated in FIG. 1G, since data can be transferred via none of the paths, the host detects an error so that the operation stops. The same goes for a case where there is already a failure in the connectivity of the path connected to the first part, CM0, when firmware replacement is started in the latter part, CM1. As is understood from the above description, if operation may stop when replacing firmware in a hot swapping manner, first, the cause of the abnormality in the path must be eliminated and then the firmware must be replaced.
For this reason, in the related art, before performing firmware replacement on the first part, the maintenance worker logs in to the host in order to issue a command to check the connectivity of the path between the storage apparatus and host. If there is no abnormality, the maintenance worker performs firmware replacement on the first part. Also, before performing firmware replacement on the latter part, the maintenance worker conducts the same work. Since this method requires execution of a command, it is necessary to secure a maintenance worker that can log in to the host with the administrator authority when replacing firmware. Also, if a great number of hosts are connected to the storage apparatus that is to perform firmware replacement, it is necessary to execute a command with respect to all the hosts so as to check the connectivity. This disadvantageously puts a heavy load on the maintenance worker. Japanese Laid-open Patent Publication No. 2005-242574 is a related-art example regarding an information processing system for automatically replacing a microprogram installed on a storage unit without having to stop operation.